On October 14, 1950, the number of countries that signed the UN Genocide Convention surpassed the 20 necessary for the convention to come into effect, which it did in January 1951. Several delegates from signatory nations: front, from left: Korea; Haiti; Iran; France; Costa Rica; rear, from left: Assistant Secretary General for Legal Affairs; Secretary General; representative from Costa Rica; and Raphael Lemkin, the Convention's chief proponent.

Not one country invoked the Genocide Convention when the Khmer Rouge regime in Cambodia caused the deaths of an estimated 1.7 million people between 1975 and 1979. Yet Cambodia itself had ratified the convention in 1950. These prisoners were interred at Tuol Sleng (Security Prison 21), a secret center operated by the Khmer Rouge in the capital, Phnom Penh.